Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-01-15
2003-10-28
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S112000, C521S130000, C521S159000, C521S170000, C521S174000
Reexamination Certificate
active
06638986
ABSTRACT:
The present invention relates to a process for the preparation of in situ-reticulated flexible polyurethane foams by reacting organic and/or modified organic polyisocyanates (a) with a special polyetherol mixture (b) and, if required, further compounds (c) having hydrogen atoms reactive toward isocyanates, in the presence of water and/or other blowing agents (d), catalysts (e) and further assistants and additives (f) with the use of silicone stabilizers.
The preparation of flexible polyurethane foams by reacting organic and/or modified organic polyisocyanates or prepolymers with compounds having a higher functionality and at least two reactive hydrogen atoms, for example polyoxyalkylenepolyamines and/or preferably organic polyhydroxy compounds, in particular polyetherols, having molecular weights of from 300 to 6000, and, if required, chain extenders and/or crosslinking agents having molecular weights of up to about 400 in the presence of catalysts, blowing agents, stabilizers, assistants and/or additives is known and has been widely described. A review of the preparation of flexible polyurethane foams is given, for example, in Kunststoff-Handbuch, Volume VII, Polyurethane, 1st Edition 1966, edited by Dr. R. Vieweg and Dr. A. Höchtlen, and 2nd Edition, 1983, and 3rd Edition, 1993, each edited by Dr. G. Oertel (Carl Hanser Verlag, Munich).
A number of industrial processes are known for the production of extremely open-cell flexible foams, i.e. reticulated flexible foams. According to Uhlig's Polyurethantaschenbuch, Hanser-Verlag, 1998, page 91, an aftertreatment of the foam with aqueous alkali solutions or a dry treatment by the Chemotronics process (destruction of the cell membranes by an oxyhydrogen explosion) may be chosen for this purpose.
U.S. Pat. No. 3,325,338 discloses reticulated ester foams. Here, the cell walls are removed by treatment in an alkaline medium. U.S. Pat. No. 5,567,740 describes a reticulated conductive flexible foam which is used as tank foam. The foam is reticulated by exposing it briefly to a flame front. U.S. Pat. No. 3,171,820 describes a process in which the cell walls of a polyurethane foam are removed by a hydrolysis process. Reticulated foams having a roughened surface are produced thereby. WO-A-8809350 is concerned with the preparation of a tank foam. This conductive foam is reticulated by the brief application of high temperatures after the actual foam preparation. DE-A-19741646 claims hydrophilic ester foams which can be reticulated by an appropriate aftertreatment.
DE-A-4420168 describes an apparatus for controlling the number of cells. In fact, a specific gas loading of the components which is intended to influence the cell size is realized. JP 11116717 describes a spongy polyurethane foam which is used, for example, as a cleaning sponge. In this case too, a considerable amount of additional air is incorporated into the polyol mixture. According to EP-A-930323, a polyurethane material is extruded with the action of a gas, a reticulated material being said to form. GB 2267840 describes in particular the use of a reticulated foam as a filter. Hydrophilic foams are used in order also to ensure an exchange of moisture. The pore size is from 0.1 to 1 mm.
In U.S. Pat. No. 3,884,848, small amounts of ester components are used, these having long carbon chains. In addition, polyetherol components are present in amounts of less than 10%. The existing incompatibility of the components is supported by a silicone stabilizer, with the result that open-cell foams can be produced. U.S. Pat. No. 4,160,076 mentions hydrophilic reticulated foams. The reticulation process is achieved in this case by a special combination of a nonionic surfactant and a liquid antifoam. In an analogous manner, U.S. Pat. No. 3,748,288 claims a polyester foam which contains small amounts of a polyetherol and amounts of a stabilizing silicone in addition to a silicone antifoam.
WO-A-9850446 describes flexible foams without cell membranes. These membrane-free foams are produced by means of special cell openers (silicone oil) which have an antifoam effect. This process is technically difficult to master since extreme foam problems can occur in the event of metering errors. In CA-A-797893, petroleum contents are said to lead to an open cell character. In U.S. Pat. No. 4,670,477, reticulated polyester foams are protected. Here, the reticulation process is attributable to the presence of small amounts of a graft polyetherol. GB 707412 describes ester foams having reticulated character. The cell opening is realized here by means of relatively long-chain polyethylene glycol components. U.S. Pat. Nos. 4,670,477 and 4,656,196 claim ester slabstock foams which contain up to 20% of a polyoxypropylene polyol or a random polyetheralcohol, graft polyetherols necessarily being used. The use of a silicone stabilizer usually used for ether foams was advantageous. According to EP-A-459622, polyethylene glycols having a low molecular weight are used as cell openers. In combination with a high molecular weight trifunctional polyetherol based on propylene oxide and ethylene oxide, reticulated foams are obtained.
CH 1354576 claims a hydrophilic foam. This is produced using a main polyol having a high ethylene oxide content and containing relatively small amounts of a propoxylated high molecular weight polyetherol. The reticulated structure is obtained by adding cell destroyers, in this case a combination of cellulose materials and in particular a silicone antifoam. In DE-A-2919372 and U.S. Pat. No. 4,259,452, a special polyol mixture consisting of a polyethylene oxide/propylene oxide-polyol comprising from 51 to 98% of ethylene oxide and a further polyethylene oxide/propylene oxide polyol having a propylene oxide content of >51% is foamed in order to obtain very open-cell foams. To ensure the reliability of the process (freedom from tears), urea is added. The water used as a blowing agent must be employed in an amount of at least 4.5 parts in order to obtain satisfactory foams. Since, in the case of the polyols used, the ethylene oxide is generally incorporated randomly, strong tin catalysts are required in order to produce a specific foam stability. It is strongly advisable to effect foaming at relatively low temperatures since the viscosity is then higher, which is to be regarded as a precondition for cell opening. This procedure is of course technologically disadvantageous. Here, the cell opening is controlled by the use of different silicone stabilizers. Thus, coarse-cell foams are obtained using stabilizers of low activity (cold-cured foam) whereas very fine-cell foams form using silicone stabilizers of high activity (hot-cured foam). In a continuation of the invention, reticulated tank foams are presented in DE-A-2038789 and GB-A-2038739. Carboxylic acids and carboxylic anhydrides are mentioned as additives—evidently in order to improve the conductivity.
U.S. Pat. No. 3,890,254 describes reticulated flexible foams which are prepared by foaming hydrophilic prepolymers using a large excess of water in the presence of a surfactant. As a result of the preparation process, the foam has a very irregular pore structure.
U.S. Pat. No. 4,052,346 discloses reticulated flexible foams based on polyesteralcohols. Antifoams, e.g. polydimethylsiloxane, are used for cell opening. Owing to the preparation method, this process is sensitive to process variations. U.S. Pat. No. 4,314,034 claims reticulated foams having high stability under damp/warm conditions. For this purpose, a hydrophilic prepolymer is reacted, the polyol component containing fibres or preferably diatomaceous earth.
DE-A-2454049 describes membrane-free open-cell flexible foams which are prepared using cell-opening fatty esters. DE-A-2210721 produces membrane-free flexible foams by using hydrophobic organosilicon compounds.
The inventions mentioned in the prior art certainly permit the preparation of open-cell or reticulated flexible foams, there being considerable potential for improvement with regard to the properties and the processibi
Falke Peter
Lutter Heinz-Dieter
Pcolinski Michael J.
BASF - Aktiengesellschaft
Borrego Fernando A.
Cooney Jr. John M.
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